Grantee Research Project Results
Final Report: Stress of Increased Sediment Loading on Lake and Stream Function
EPA Grant Number: R825433C028Subproject: this is subproject number 028 , established and managed by the Center Director under grant R825433
(EPA does not fund or establish subprojects; EPA awards and manages the overall grant for this center).
Center: UC Davis Center for Children's Environmental Health and Disease Prevention
Center Director: Van de Water, Judith
Title: Stress of Increased Sediment Loading on Lake and Stream Function
Investigators: Goldman, Charles R. , Reuter, John E. , Stubblefield, Andrew P. , Hatch, Lorin
Institution: University of California - Davis
EPA Project Officer: Packard, Benjamin H
Project Period: October 1, 1996 through September 30, 2000
RFA: Exploratory Environmental Research Centers (1992) RFA Text | Recipients Lists
Research Category: Center for Ecological Health Research , Targeted Research
Objective:
The overall objective of this research project was to investigate phosphorus (P) and sediment loading in watersheds of the Lake Tahoe Basin. Since about 1980, P has become nutrient factor limiting for algal growth in the lake. The objective of the first study was to evaluate P transport to Lake Tahoe from many of its major tributaries. Specifically, we looked at the generation, transport, and fate of P in Lake Tahoe streams; P dynamics at the single-watershed scale; and the effect of stream P on phytoplankton. The objective of the second study was to identify source areas of suspended sediment, mechanisms and processes involved in mobilizing suspended sediment, and the timing and dynamics of suspended sediment delivery in the subalpine environment of the Lake Tahoe Basin. We primarily chose volcanic watersheds on the west shore of Lake Tahoe (Ward and Blackwood Creeks) as our study sites. The watersheds are 25 and 29.5 km2, respectively, rising to subalpine elevations of 2,700 m. Both watersheds are listed by the State Water Resources Control Board as "impaired" because of excessive sediment and nutrient loading.
Summary/Accomplishments (Outputs/Outcomes):
The results from the first study indicate that P delivery (concentrations, loads, and nutrient ratios) changes greatly at interannual, seasonal, and spatial scales. Annual and seasonal P concentrations varied from three to five orders of magnitude (1,000- to 10,000-fold) in a given stream and were strongly associated with total suspended solids (TSS). Hydrologic events (rain on snow, spring snowmelt) produced the highest P concentrations. However, streams with the highest annual P concentrations did not necessarily have the highest annual P loads.
In addition, we estimated expected total phosphorus (TP) load in Ward Creek in the absence of human development. We also determined that some forms of P may remain suspended in the lake’s photic zone for extended periods of time, increasing the opportunity for phytoplankton and bacterial uptake.
In the second portion of our project (concerning sediment load), we used instantaneous sediment loading data for the period 1982-2000, and we ranked several sediment source areas. The correct ranking of these areas allows management agencies to prioritize restoration projects.
We also developed a convenient method for monitoring sediment-related water quality in subalpine environments, often a difficult task because of rugged and inaccessible terrain and huge daily and seasonal variations in discharge and sediment concentration. Continuous turbidity monitoring with nephelometric turbidometers has been effectively used in other environments, so we adapted these methods for our subalpine work, considering turbidity to be a proxy for suspended sediment and P. We found excellent regressions for turbidity and suspended sediment, indicating that this method is a valid approach for water quality monitoring in subalpine environments, as long as the findings eventually can be field validated.
In the second study, we evaluated the effect of hysteresis on sediment-load monitoring methods, finalized a 3-year study identifying erosional "hot spots" (high sediment source areas) with a network of nine nephelometric turbidometers, and summarized the results from different types of geomorphologic measurements as compared to results from the monitoring snowmelt sediment load.
The following activities were accomplished:
• We determined sources of P and sediment in various Lake Tahoe watersheds. This information assists environmental management agencies in prioritizing restoration projects, and provides essential information for our transparency model.
• We correlated TSS, TP, and particulate phosphorus (PP) concentrations with geological surficial soils, indicating that stream sediment and PP may be coming from near-stream or instream sources. Watershed-based parameters related to human disturbance, however, were not well correlated with stream P.
• P delivery (concentrations, loads, and nutrient ratios) changes greatly at interannual, seasonal, and spatial scales. Annual and seasonal P concentrations varied up to three to five orders of magnitude (1,000- to 10,000-fold) in a given stream and were strongly associated with TSS. P loading was greatest during spring snowmelt when discharge is maximum. In a climate such as Lake Tahoe, which is largely dry during the summer and fall, nutrient and sediment control needs to be focused on the hydrologically "active" time of year. Year-to-year differences in precipitation (as snow and/or rain) are a critical driving force in controlling interannual variation in P and sediment loading from the watershed. Management agencies can use this information to better plan the timing of sediment loading control efforts.
• Hydrologic events (rain on snow, spring snowmelt) produced the highest P concentrations. However, streams with the highest annual P concentrations did not necessarily have the highest annual P loads. Water quality standards for stream tributaries at Lake Tahoe largely are designed to protect the beneficial uses of the lake itself. Water quality in Lake Tahoe is influenced more directly by load than concentration, therefore, a total maximum daily load for P, nitrogen, and fine sediment (< 63 µm) currently is being developed to determine allowable load.
• Using a sensitive bioassay technique, we detected no changes in soluble P concentrations along a single stream, suggesting that P associated with particles larger than 63 µm (i.e., sand size) may settle out of the lake photic zone before P utilization can occur. Low-mass P compound (less than 63 µm) and dissolved P may remain suspended in the photic zone for extended periods of time. This longer residence time in the photic zone, where active algal growth occurs, increases the opportunity for phytoplankton and bacterial uptake of P. This finding may be useful to other researchers investigating the nutrient budget of Lake Tahoe.
• Our particle-size treatment results imply that 75-90 percent of the bioassay response resulted from P in the sub-0.45 µm range (i.e., dissolved). This study highlighted the importance of evaluating the biologically available P component of TP in stream flow. To be effective, restoration practices must focus on the control of the most biologically active forms of P.
• We determined that turbidometry appears to be an effective tool for measuring sediment and nutrient fluxes in the dynamic conditions found in subalpine environments. In environments where runoff is flashy and sampling difficult, this technique offers investigators a viable solution, as long as the findings can be field validated.
• We determined that continuous monitoring of stream networks can provide insight into sediment source areas that were not possible from routine sampling approaches. The identification of sediment sources is critical in planning watershed restoration activities, and in setting priorities of erosion control projects. The installation of continuous monitoring stations can be very effective in providing resource managers with a more accurate determination of sediment source.
Supplemental Keywords:
ecosystem, ecosystem protection, environmental exposure and risk, geographic area, international cooperation, water, terrestrial ecosystems, aquatic ecosystem, aquatic ecosystem restoration, aquatic ecosystems and estuarine research, biochemistry, ecological effects, ecological indicators, ecological monitoring, ecology and ecosystems, environmental chemistry, restoration, state, water and watershed, watershed, watershed development, watershed land use, watershed management, watershed modeling, watershed restoration, watershed sustainability, agricultural watershed, exploratory research environmental biology, California, CA, Clear Lake, Lake Tahoe, anthropogenic effects, aquatic habitat, biogeochemical cycling, ecological assessment, ecology assessment models, ecosystem monitoring, ecosystem response, ecosystem stress, environmental stress, environmental stress indicators, fish habitat, hydrologic modeling, hydrology, integrated watershed model, lake ecosystems, lakes, land use, nutrient dynamics, nutrient flux, water management options, water quality, wetlands., RFA, Scientific Discipline, INTERNATIONAL COOPERATION, Water, ECOSYSTEMS, Ecosystem Protection/Environmental Exposure & Risk, Water & Watershed, Aquatic Ecosystems & Estuarine Research, Restoration, Aquatic Ecosystem, Fate & Transport, Environmental Microbiology, Monitoring/Modeling, Terrestrial Ecosystems, Biochemistry, Ecology and Ecosystems, Aquatic Ecosystem Restoration, Watersheds, fate and transport, watershed management, sediment transport, restoration strategies, stream function, watershed influences, hydrology, wetland restoration, integrated watershed model, aquatic ecosystems, environmental stress, source load modeling, watershed sustainablility, Sierra Nevada, ecosystem stress, ecology assessment models, ecological impact, aquatic habitat protection , land use, ecological researchRelevant Websites:
http://ice.ucdavis.edu/cehr/ Exit
Progress and Final Reports:
Original AbstractMain Center Abstract and Reports:
R825433 UC Davis Center for Children's Environmental Health and Disease Prevention Subprojects under this Center: (EPA does not fund or establish subprojects; EPA awards and manages the overall grant for this center).
R825433C001 Potential for Long-Term Degradation of Wetland Water Quality Due to Natural Discharge of Polluted Groundwater
R825433C002 Sacramento River Watershed
R825433C003 Endocrine Disruption in Fish and Birds
R825433C004 Biomarkers of Exposure and Deleterious Effect: A Laboratory and Field Investigation
R825433C005 Fish Developmental Toxicity/Recruitment
R825433C006 Resolving Multiple Stressors by Biochemical Indicator Patterns and their Linkages to Adverse Effects on Benthic Invertebrate Patterns
R825433C007 Environmental Chemistry of Bioavailability in Sediments and Water Column
R825433C008 Reproduction of Birds and mammals in a terrestrial-aquatic interface
R825433C009 Modeling Ecosystems Under Combined Stress
R825433C010 Mercury Uptake by Fish
R825433C011 Clear Lake Watershed
R825433C012 The Role of Fishes as Transporters of Mercury
R825433C013 Wetlands Restoration
R825433C014 Wildlife Bioaccumulation and Effects
R825433C015 Microbiology of Mercury Methylation in Sediments
R825433C016 Hg and Fe Biogeochemistry
R825433C017 Water Motions and Material Transport
R825433C018 Economic Impacts of Multiple Stresses
R825433C019 The History of Anthropogenic Effects
R825433C020 Wetland Restoration
R825433C021 Sierra Nevada Watershed Project
R825433C022 Regional Transport of Air Pollutants and Exposure of Sierra Nevada Forests to Ozone
R825433C023 Biomarkers of Ozone Damage to Sierra Nevada Vegetation
R825433C024 Effects of Air Pollution on Water Quality: Emission of MTBE and Other Pollutants From Motorized Watercraft
R825433C025 Regional Movement of Toxics
R825433C026 Effect of Photochemical Reactions in Fog Drops and Aerosol Particles on the Fate of Atmospheric Chemicals in the Central Valley
R825433C027 Source Load Modeling for Sediment in Mountainous Watersheds
R825433C028 Stress of Increased Sediment Loading on Lake and Stream Function
R825433C029 Watershed Response to Natural and Anthropogenic Stress: Lake Tahoe Nutrient Budget
R825433C030 Mercury Distribution and Cycling in Sierra Nevada Waterbodies
R825433C031 Pre-contact Forest Structure
R825433C032 Identification and distribution of pest complexes in relation to late seral/old growth forest structure in the Lake Tahoe watershed
R825433C033 Subalpine Marsh Plant Communities as Early Indicators of Ecosystem Stress
R825433C034 Regional Hydrogeology and Contaminant Transport in a Sierra Nevada Ecosystem
R825433C035 Border Rivers Watershed
R825433C036 Toxicity Studies
R825433C037 Watershed Assessment
R825433C038 Microbiological Processes in Sediments
R825433C039 Analytical and Biomarkers Core
R825433C040 Organic Analysis
R825433C041 Inorganic Analysis
R825433C042 Immunoassay and Serum Markers
R825433C043 Sensitive Biomarkers to Detect Biochemical Changes Indicating Multiple Stresses Including Chemically Induced Stresses
R825433C044 Molecular, Cellular and Animal Biomarkers of Exposure and Effect
R825433C045 Microbial Community Assays
R825433C046 Cumulative and Integrative Biochemical Indicators
R825433C047 Mercury and Iron Biogeochemistry
R825433C048 Transport and Fate Core
R825433C049 Role of Hydrogeologic Processes in Alpine Ecosystem Health
R825433C050 Regional Hydrologic Modeling With Emphasis on Watershed-Scale Environmental Stresses
R825433C051 Development of Pollutant Fate and Transport Models for Use in Terrestrial Ecosystem Exposure Assessment
R825433C052 Pesticide Transport in Subsurface and Surface Water Systems
R825433C053 Currents in Clear Lake
R825433C054 Data Integration and Decision Support Core
R825433C055 Spatial Patterns and Biodiversity
R825433C056 Modeling Transport in Aquatic Systems
R825433C057 Spatial and Temporal Trends in Water Quality
R825433C058 Time Series Analysis and Modeling Ecological Risk
R825433C059 WWW/Outreach
R825433C060 Economic Effects of Multiple Stresses
R825433C061 Effects of Nutrients on Algal Growth
R825433C062 Nutrient Loading
R825433C063 Subalpine Wetlands as Early Indicators of Ecosystem Stress
R825433C064 Chlorinated Hydrocarbons
R825433C065 Sierra Ozone Studies
R825433C066 Assessment of Multiple Stresses on Soil Microbial Communities
R825433C067 Terrestrial - Agriculture
R825433C069 Molecular Epidemiology Core
R825433C070 Serum Markers of Environmental Stress
R825433C071 Development of Sensitive Biomarkers Based on Chemically Induced Changes in Expressions of Oncogenes
R825433C072 Molecular Monitoring of Microbial Populations
R825433C073 Aquatic - Rivers and Estuaries
R825433C074 Border Rivers - Toxicity Studies
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